1. Technical Field:
This invention relates to a method and agents for producing exceptionally clean steel for continuous casting and the like.
2. Description of the Prior Art:
The prior art methods and agents heretofore used for the cleansing of steel of non-metallic inclusions are represented by U.S. Pat. Nos. 2,221,784, 4,036,635, 4,217,134, 4,238,227 and 4,290,173.
U.S. Pat. No. 2,221,784 discloses the use of additive agents containing silicon, calcium, aluminum and at least one metal selected from the group consisting of titanium and zirconium, the additive being added to the molten steel in the ladle.
U.S. Pat. No. 4,036,635 discloses a steel melt formed under an iron oxide containing slag held back while the steel melt is tapped and subjected to deoxidation with silicon or aluminum plus an after treatment with a calcium containing substance such as calcium silicon or calcium carbide.
U.S. Pat. No. 4,217,134 discloses the use of compositions comprising lime, fluorspar, and ground aluminum used in a method of desulphurizing molten steel by adding the compositions to the steel in the ladle or injecting the composition in particulate form into the molten steel.
U.S. Pat. No. 4,238,227 discloses the use of a high amount of aluminum added to the tap ladle before the first one-third volume of steel is tapped and then adding conventional deoxidizers while the final two-thirds volume of steel is tapped. Argon gas is subsequently blown through the steel.
U.S. Pat. No. 4,490,173 discloses the use of additive compositions for flux solubilization, desulphurization and the removal of inclusions. The additive composition includes lime and a compound selected from the group consisting of bauxite and mixtures of calcium alimunate and bauxite.
The present invention eliminates the several problems generally associated with the prior art methods and additives used in attempting to produce a clean steel particularly suited for use in a continuous caster and incidentally reduces the amount of aluminum as a deoxidizing agent to approximately one-half of the amount theretofore believed necessary.